lrfigueroa

Since you probably be taking wildlife pics, I would get a 2X converter which will double the focal length of you current 80-200mm or if you want to upgrade to an "L" lens you can not go wrong with the Canon EF100-400 L F4.5-5.6 IS lens and get its 2X converter which are both with manufacturer's discount right now. It also depends on the final quality you might want to get or if you are planning to enlarge some pics etc....I would recommend a decent tripod to take.

For lenses, For the short side, I'll take high quality primes such as Zeiss 21/2.8 (won't find anything better in that range) and a fast 50mm (if possible the Zeiss 50/2 Makro planar so you can take some nice macros as well!).

For the longer side I'll take a 70-200 f4 IS with a 1.4 and a 2x extender just in case. You are pretty well covered and it is a light setup that you can fit in a small bag (it's what I have btw). Except the Zeiss, pretty easy to get them all second hand.

Or

Get a Canon 16-35II + 50mm + 70-200 F4 IS with the extenders

or

replace the 70-200 in any of the setups above with the Canon 100-400 to cover more wildlife.

Note on the 50mm: go either Zeiss 50/2 or Canon 50L 1.2: they will be useful for Macro (the Zeiss) or night star shots

In any of these cases you're all set with just 3 good lenses, just remember to get nice B+W polarisers for each of them

I have been to Namibia many times. Unless you plan to go to Etosha or the Skeleton Coast and associated Namib Desert behind the Skeleton Coast, you won't need a long lens and up to 400mm will do nicely which ever way you reach that focal length (70-200 and 2X or 100-400). However you will ache for a longer lens for some wildlife in Etosha or if you get onto the desert elephants.

You are correct that the scenery is spectacular and short lenses are a must.

As a suggestion, the 24-105 and 100-400 would allow you to cover a huge range with just two lenses but the options are so broad it is mostly up to your personal preference.

What camera gear you take depends a little on your approach to travel - some prefer to travel light. Either way, I wouldn't go without a short lens. A circular polarising filter is probably a must-have - and won't take up much space!

Weather-sealed equipment is nice for the dust, especially in places like Etosha. With due care, however, you can make do with less resilient gear. - My EOS650 did just fine in the Fish River Canyon.